An apparatus and method for abrading the edges of rigid materials such as glass plates is described whereby opposing edges of different glass plates are simultaneously abraded using a single grinding wheel.
Various types of motor driven grinding machines have been available for many years in the glass and other industries whereby sheets or plates of various rigid materials are driven by conveyors and are stopped, clamped and ground (seamed) to remove rough, uneven and jagged edges. The grinding or abrading of the edges is also performed with glass sheets prior to heat tempering where edge uniformity is a requirement. U.S. Pat. Nos. Re. 29,097; 4,633,408; 4,739,586; 4,817,339 and 3,800,477 demonstrate various types of grinding apparatus and methods for processing or seaming the edges of glass with automated equipment.
Tile, stone, ceramics and other planar materials have been processed in the past with one grinding wheel utilized for each glass plate or other planar material. In certain seaming techniques the edges of glass plates are drawn across an abrasive belt system with the belts mounted at forty-five degree angles. Another prior art technique uses full edge grinding whereby glass plates are transported by a conveyor over a bank of grinding wheels of progressively finer abrasive size. Also, double edge grinding machines are currently used whereby glass plates are passed along a horizontal conveyor with a parallel banks of grinding wheels on each side of the glass plates.
Certain of the techniques and methods which are presently employed are time consuming and inaccurate or require precise adjustments for the particular size and thickness of the glass processed. Other disadvantages include extensive labor and handling, often causing high rejection rates. Certain of the prior art grinding techniques require highly accurate measurements be taken for different sizes and thicknesses of the glass sheets being processed and often rely on the skill of the particular operator to obtain an acceptable product.
Thus, with the problems and disadvantages of prior art methods of the various apparatus known, the present invention was conceived and one of its objectives is to provide edge grinding apparatus for rigid planar materials such as glass which is easy to set up and operate by relatively unskilled personnel.
It is yet another objective of the present invention to provide a method for grinding rigid materials whereby opposing edges of different materials are simultaneously abraded using a single grinding wheel.
It is yet another objective of the present invention to provide a method for grinding rigid materials which is automated for rapid, accurate production.
Various other objectives and advantages of the present invention will become apparent to those skilled in the art as a more detailed description is set forth below.
The invention as described includes apparatus and a method designed to automatically abrade all four sides of a rigid rectangular material such as glass plates along a horizontal plane without operator intervention and without the need for measurement of sizes or special machine calibration. The invention involves using one grinding wheel to simultaneously grind two edges of two different rigid planar materials such as glass, stone, ceramic or otherwise.
In a typical method of the invention a first planar glass material is placed on a first horizontal roller conveyor and is transported to a series of stops located therealong. When the leading (lateral) edge of the first planar material has located against the stops, a pneumatic clamping pressure bar system (usually one above and one below the planar material) is actuated to clamp the first planar material in position. With the first planar material now clamped, the roller conveyor is deactivated and the stops are retracted. A motor driven spindle holding a xe2x80x9cVxe2x80x9d formed diamond grinding wheel or other standard configuration such as a pencil edge wheel which is located on a motorized cross slide is now motor driven from right to left causing the periphery of the grinding wheel to come into contact with the leading (lateral) edge of the first planar material and to pass along its full leading edge dimension. An appropriate water feed from a recycling tank provides cooling action on the grinding wheel as it makes the traverse. The planar material now has a seamed leading edge. The motor driven spindle has now moved to the left side of the conveyor.
Next, the pneumatic clamps for the leading edge of the first planar material retract and the roller conveyor is reactivated causing the first planar material to be moved forward. A proximity sensor registers the passage of the first planar material and when it has fully exited the first conveyor and is on a second conveyor, a signal is given to reverse the second conveyor""s direction. The planar material is now driven backward, toward the grinding wheel located between the two conveyors where a stop and clamp system causes the first planar material to locate against the stop and to be fixed in that position on the second conveyor by clamps as before. At this point, the lateral trailing edge of the first planar material is presented to the grinding wheel as the first planar material rests on the second conveyor.
During the time in which the first planar material is driven forward and then reversed, the next or second planar material which may be of different dimensions is moved by the first conveyor into the space recently evacuated by the first planar material. The second planar material comes into contact with the stop system and is clamped in place on the first conveyor.
At this point, while the first planar material is presenting its lateral trailing edge to the grinding wheel the second planar material is presenting its lateral leading edge to the same grinding wheel. The grinding wheel is now activated and it makes a pass from left to right causing the periphery of the grinding wheel to contact the lateral trailing edge of the first planar material and the lateral leading edge of the second planar material simultaneously. Afterwards, the grinding wheel resides at the right side, between the two conveyors. The clamps are released and the first planar material is evacuated in a forward direction by the second roller conveyor. Once evacuated, the second planar material now moves to the second conveyor as earlier described to take the place of the first planar material. Meanwhile the third planar material is now loaded onto the first conveyor and the sequence of operation of simultaneous dual material abrading is repeated at the first grinding wheel.
The first planar member is accelerated from the second conveyor into a right angle transfer system (drop-down belt system). The first planar member is now conveyed at a right angle to its original direction of transport and is processed through an identical second grinding wheel apparatus whereby the longitudinal edges of the planar material are likewise abraded as described above. When completed all four sides of the first planar material have been abraded and are ready for heat tempering or other processing. The operation continues for the second and all subsequent planar materials as required.